/Engine/Source/Runtime/GeometryCore/Public/Deformers/Kelvinlets.h
The canonical Kelvinlet for a regularized force. u(r) = [A_e(r) I + B_e(r) r r^t] f; where A_e(r) = (a-b)/r_e + a e^2 / (2 r_e^3) B_e(r) = b / (r_e^3)
FVector3d Evaluate ( const FVector3d & Pos ) const